Operation of the by-product recovery system of a coal distillation plant



5. P. MILLER ATTORN EYS S, F. MILLER OPERATION OF THE BY-PRODUCT RECOVERYy SYSTEM OF A COAL DISTILLATION PLANT Filed Sept. 25, 1929 2 Sheets-Sheet 2 Imm..

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INVENTOR BY 7m.;

ha/faudra@ ATTORNEYS Patented Jan. 16, 1934 PATENT orf-ica oPEaA'rroN oF 'ma Br-PnoDUc'r RE- covanr SYSTEM or A com. DIs'rmLA- TION PLANT Stuart Parmelee Miller, Englewood,` N. J., as-

signor to The Barrett Company, New York,

N. Y., a corporation of New Jersey Application September 25, 1929 Serial No. 395,118

. i6 laims.

This invention relates 'to a new method oi operating the by-product recovery system of a coke oven battery, whereby a product suitable for fuel is obtained and a distillate with a high a tart acid content isv produced. .The invention includes both thev method of operation and apparatus therefor.

This application is in part a continuation o the applicants copending application Serial No. lo -3l6,8$4, iled November 3, 192B.

Where coke oven plants are operated by steell companies, the coke produced at the coke oven plant is commonly used in the blast furnaces of the steel company and the tar producedat the colse oven plant isL commonly used' as fuel in the steel mill, particularly as fuel ,in open hearth or other furnaces. Any surplus of tar produced at the coke oven plant in excess of that required as fuel in the steel mills is comgg monly sold as tar and is shipped to tar distillaz,

tion plants and there distilled for the production oi distillate oils and pitch. The distillate oils have considerably greater value than the tar itself but the pitch has relatively much less value and in some cases presents a problem in its ,disposal y The present invention provides an improved process of operating the by-product recovery system of a coke'oven battery and is particu- 3@ larly applicable to coke ovenbatteries which are operated `in connection with steel mills.

The new method-of operation. provides a clean oil product in addition to aV product suitable for fuel. The coke oven. gases are fractionally g5 cooled to produce a heavy tar and a lighter tar or tarry oil and the tarry oil is distilled to prolduce aV clean oil distillate and pitch, and the pitch is blended with the heavy tar and used for fuel. By fractionally cooling the gases and 4@ distilling only the lighter tar or tarry oil, less material need be distilled to produce the same amount of tar acid than would be necessary on distilling the total tar produced by blending the various tai-s separated from the gases at a colte oven battery, and the percentage of lower boiling tar acids in the distillate is increased.

According to the ordinary operation of a coke oven battery, the gases from the various ovens are collected in a gas-collector main and are cooled therein and a heavy tar is separated from the gases. The gases then pass to a condensing system wherel further tar, which is a lighter tar or tarry oil, is separated from the gases. The

heavy tar and tarry oil are mixed together to liquor.

form the tar of commerce, 4and are largely used as a fuel at steel mills.

The gas collector main 'of the battery must be so operated that pitch and colse do not accumulate within the collector main and obstruct the passage of. gases through lthe main. According to one usual method of operating the gas collector main, the gases are sprayed with ammonia liquor and the ammonia liquoris supplied in such quantity that the bottom of the collector main is ushed with the liquor and heavy tarry/ matter which separates from the gases in the main owing to the cooling and scrubbing action of 4 the kamnfionia liquor is vwashed from the main. This heavy tar, to- 7@ gether with the ammonia liquor, is drawn ofi from themain to a decanter and the heavy tar and ammonia liquor are separated by decontation. Instead of blending the heavy tar from the collector main with the tarry oil from the 'it condensers, according to this invention the heavy-tar 'and tarry oil are` kept separate and the tarry oil is distilled and the pitch produced isblended with the heavy tar and used for fuel.

Instead of spraying the gases with ammonia liquor it is customary; according to a different method of operating the collector main, to flush the main with a mixture of tar and ammonia This prevents the accumulation of tar and pitch deposits in the main. Any tar which separates from the gases in passing through the main, owing to the cooling effect of the material used for flushing the main or from other causes, is Washed out oi the main together with the material used for ilushing the main. This mixture of tar and ammonia liquor is blended with the tarry oils from the condensing system and whatever ammonia liquor may be present with these terry oils and the combined tar and ammonia liquor mixture thus formed is used for ushing the main. According to the modiiied method contemplated by this invention in which the tarry oilfrom the condensers and the heavy tar from the collector main are separately collected and the tarry oil is distilled, the collector main may be kept free from pitch deposits by iiushing the bottom of the main with the heavy tar which is collected from the collector main and to which ammonia liquor may be added. Ammonia liquor may be sprayed into the main in regulated amount to cause the separation of the desired amount of tar from the gases. Various means of operating the collector main to regulate the llt Vtemperature of the gases and produce a heavy tar may be employed.

According to this invention, whatever they ma'- terial employed for ushing the collector main and controlling the temperature of the gases in this main, the heavy tar from the collector main and the tarry oil from the condensers are separately collected. The tarry oil is distilled and the pitch thus produced is blended with the heavy tar for use as fuel.

The gases are partially cooled in the collector main and `heavy tar is separated from them. After leaving the collector main the gases are further cooled to separate further tar which is a lighter tar or tarry oil. This further cooling of the gases may be effected in a single condenser or fractional condensers. The condensers may be direct condensers or .indirect condensers. Various methods of separating the tarry oils from the gases may be employed. By proper regulation of the operation of the collector main and the condensing system, the general character of the tarry oil product obtained can be controlled.

The higher boiling constituents present in the gases as they leave the ovens are separated in the collector main during the initial cooling of the gases. Tar acids boil at relatively low temperatures and a large proportion of the tar acids are carried from the collectormain in the vapor state, and are removed from the gases in the condensing system. The lighter tar or tarry oil of relatively low boiling range which isseparated from the gases in the condensers will ordinarily have a relatively high tar-acid content. Where the operation of the collector main is such that the gases leave at a high temperature, the resulting gases may advantageously be cooled in two stages to produce a tarry oil of higher boiling range and a tarry oil of lower boiling range. The boiling range of the lighter tarry oil may be so controlled as to yield a tarry oil .of high tar-acid content.`

According to this invention the tarry oil or a tarry oil fraction is distilled to produce pitch and a distillate oil from which the tar acids are ex tracted. The total tarry oil distillate may be extracted for tar acids or a fractional distillate, high in tar acids, may be extracted for its tar acid content.

When the recovery of naphthalene is desir? able, naphthalene may be separated from the oil distillate after extraction to remove the tar acids by chilling to cause separation of the naphthalene or by any other suitable method such as the methods employed-for the removal of naphthalene from coal tar distillate.

The neutral oil remaining after the extraction of tar acids from the distillate may be blended with tar or tarry oil in the manufacture of creosoting composition. Where two or more clean oil distillates are obtained, of which only the lower boiling distillate is extracted for tar acids, the neutral oil remaining may be blended with the distillate fraction of higher boiling range to produce a clean creosote oil. The neutral oil and the higher boiling distillate may be together blended with a tar, such as a tarry oil, to produce a creosoting composition.

Various types of stills may be employed for distilling the tarry oil to pitch. The distillation may be carried to various extents to produce oils of desired boiling range and pitches of various melting points. A lower melting point pitch may be produced or the distillation may be acarreo so carried out as to produce a pitch of high melting point, as, for example, a pitch with a melting point of A400 F. or higher. According to this invention the pitch produced is blended with tar romthe collector main. A lower melting point pitch may be readily blended with heavy tar from the collector main. However, where a higher melting point pitch is produced, care must be taken in blending the tar and pitch in order to prevent the pitch from separating irom the tar. The pitch and tar are preferably blended while the pitch is still hot and the blending may be effected by running a stream of the tar and a stream of the pitch continuously into a mixing tank and directing the two streams toward one another in such a way that as they enter the tank they mix with one another before they mix with the blended product already in the mixing tank. The two streams may be directed toward one another at a relatively sharp angle and they may be brought together with considerable force so that they mix to a considerable extent before mixing with the contents or the mixing tank. Suitable agitating means may be provided within the tank. The resulting product is maintained at a sufciently high temperature to keep itin a thin uid condition, so that it can be pumped to burners for use as fuel. l

An ordinary pipe coil still may be employed for distilling the tarry oil in which case the heated tar will be p assed to a vapor chamber where the vapors will be separated from the undistilled residue. Where desirable, two or more pipe coil stills or coils may be used in series and the residue from the vapor chamber connected with the first pipe coil still or coil further heated and distilled in the next pipe coil still or coil. When operating according to this u method, the lighter distillate from the first distilling operation may be separately collected from the higher boiling distillates from the succeeding distillation stages.

The rst distillate will usually be high in tar acids and may advantageously be treated for their recovery.

According to a preferred method, the tarryoil is distilled by being brought into direct contact with hot coke oven gases. Various means for doing this are possible. According to an advantageous method of operating such a still, the hot gases and vapors coming from the still are employed for preheating and also partially distilling the tarry oil so that on passing the tarry oil to a vapor box before bringing it into direct contact with the hot gases in the still, lighter vapors may be removed from the tarry oil in the vapor box. Such vapors are rich in tar acids. By removing lighter vapors from the tar before bringing it into direct contact with the hot coke oven gases, the dimcult'ies involved in separating such light vapors from the gases may be avoided. y

The invention will be further described in connection with the accompanying drawings, but it is intended and is to be understood that it is not limited thereto.

Fig. l is a plan view of a coke oven battery equipped for carrying out this invention;

Fig. 2 is an elevation partly in section of a of Fig. l; and

Fig. 3 is a section on the line 3 3 of Fig. 2.

The coke oven battery 5 is connected through uptake pipes and goose-necks 6 with a collector main 7. The gases from the collector main pass through the cross-over main 8 to the condensers 9. The gases are partially cooled in the goose-necks and collector main by ammonia liquor sprayed through the nozzles 7', and the tar which separates from the gases is drawn oi into the decanter 10 and from there into the heavy tar storage tank 1l.

The condensers 9 may be direct condensers or indirect condensers. Direct condensers are here shown. The tarry oil separa-ted in the condensers together with the ammonia liquor present are drawn ol into the decanter 17 and from there the tarry oil is separated into the tank 18. Several tarry oil fractions may be collected, although according to the method described in connection with the drawings, the recovery of but one tarry oil fraction is contemplated.

In the drawings the means shown for distilling the tarry oil is a still in which the tarry oil is brought into direct contact with hot coke oven gases. Several ovens of the battery 5 are provided with uptake pipes and goose-necks which are located at the ends of these ovens opposite to theusual uptake pipes 6. By proper manipulation of valves in the uptake pipes and goosenecks 20 and the corresponding values in the uptake pipes and goose-necks 6, the gases from there ovens may be directed to the hot gas header 21 or to the collector main 7. The hot gases pass through the hot gas header 21 into the still 22 and thence up through the tower 23 and the main 24 into the heat interchanger or condenser 25, thence through the main 26 into the condenser 27, and from there into an exhauster 28 which may be the same exhauster as that employed for drawing the gases through the collector main 7 and condenser 9. Beyond the exhauster means for the recovery of ammonia and light oils may be located.

In order to maintain the gases employed for distillation, at a high temperature and to prevent lors of heat through radiation the uptake pipes and goose-necks 20, the hot gas header 2l and the still 22 are advantageously insulated as indicated in the drawings; and also other units of the equipment such as the tower 23 are preffrom. the still through the trap 33.A The pitch from the still is blended directly with the heavy tar from the collector main and this tar may be somewhat heated before blending with the pitch although this will depend upon the temperature and melting point of the pitch and the temperature of the tar.

The tar from the collector mainemay be blend-A ed with the pitch by pumping it through the line 34 by the pump 35 to the mixing tank and causing it to mix with the pitchfrom the still supplied through line 36 by causing the stream of the tar and the stream of the pitch entering the tankto mix with each other before they mix with the blended material inthe tank. If the pitch and tar are partially mixed before they mingle with .the contents of the tank, a homogeneous mixture may readily vbe produced in the mixing tank. The tank 37 may be provided with agitating means to aid in the blending of the tar and pitch. A condenser 38 is provided for condensing any vapors which may rise from the ymixing tank. Any condensate produced in this condenser may be returned to the mixing tank or it may be drawn od as a separate product. The mixing tank may be provided with a steam coil 39. The mixture of tar and pitch is drawn off into a storage tank 40 in which it may be maintained in a thinly fluid condition by the steam coil al. From this tank it is pumped through the line 42 to burners where it is used as fuel.

The tarry oil from the condensers 9 may be pumped directly into the still 22 although it is advantageously first preheated by pumping it by means of pump 45 through the lin'e 46 and the coil 47 in the heat interchanger 25. The heated tar is passed from this coil into the vapor box e8 and distilled. The vapors from the vapor box pass to the condena-cree and the clean oil distillate, which is a distillate of low boiling range, is collected in the storage tank 50. Residue from the vapor box is pumped to the still through the line 51 by the pump 52. lt is advantageously sprayed into the gases and vapors passing up through the tower 23, although it may be admitted directly to the still 22. A portion of the residue from the vapor box 'a8 may be collected in tank 13.

According to the drawings, this partially distilled tar from which the lowest boiling constituents have been removed in the vapor box is sprayed through the nozzle 53 into the hot gases and vapors rising through the .towerl 23. Baies 54 and 55 are provided above and below the nozzle for preventing the entrainrnent of tar spray in the gases leaving the tower. Where a high melting point pitch, e. g., a pitch with a melting point of 350 F. or 400 F. or higher is to be made in the still, the preheated and partially distilled tar which collects in the bottom of the tower 23 is advantageously conducted through the pipe 54 to the end of the still at which the gases enter from the hot gas header 21. The tar and hot gases thus are passed through the still in a concurrent direction and the nished product is drawn oi through the trap 33 and levelling arm 32 and blended with the heavy tar from the collector main, as previously described.

The agitating means described is designed to throw an intense spray of tar up into the gases in the vapor' space of the still. This intense spray of tar scrubs the gases and removes entrained impurities so that the gases and vapors leaving the still through the main 24 .enter the condensing system substantially free from entrained impurities. The heavier oil vapors will be separated from the gases in the condenser or heat interchanger 25, and a heavy clean oil product will be collected in the tank 56. The lower boiling vapors will be separated from the gases in the vcondenser 27, and may be withdrawn into the storage tank 57 as a lighter `clean oil. The "condenser 27'/ may be a direct or indirect condenser. The clean oil distillate in the tanks 50, 56, 57, or in any two of these tanks, may be blended.

The distillate recovered in the tanks 50 and 57 is of lower`boling range and this may advantageously be blended and treated for the extraction of tar acids' or only the lower boiling distillate in the tank 50 may be so treated. This light clean distillate is run o at intervalo thru I 7 thru the une 64.

The extraction tank 62 is supplied with agitating means 65. After suitable agitation of the caustic soda or other alkaline solution employed for the extraction of tar acids and the clean oil distillate of relatively high free acid content, the contents of the tank are allowed to settle.

' The neutral oil resulting from the extraction separates from the aqueous solution of tar acid salts. Thevalve 66 is opened and the contents of 62 are drawn off thru the sight box 67 and separately collected: the neutral oils in the tank 69 and the aqueous solution in the tank 70. The latter is worked up for the recovery of tar acids. The neutral oil in 69 may be pumped thru the line '72 to be blended with the tar and pitch in the tank 37, and used for fuel; or this neutral oil may be blended with the clean oil in the tank 56 and used for creosote. The clean oil from ,57 may be added to this creosote solution. Clean. oil from these sources may be blended with tarry oil from i8 or heavy-tar from ll to form a solution suitable for creosoting purposes.

Depending upon the amount of fuel required and the other market conditions, the method of operation may be somewhat altered. According to this invention, however, heavy tar from the collector main is blended with pitch for fuel.

'The pitch is obtained by distillation of tarry oil from the ccndensers.

The invention may b'e carried out in existing equipment with but slight alteration except for the installation of the still. Where a coke oven plant is employed in connection with a steel i I mill, the existing plant may be altered as herein disclosed in order to produce fuel and in addition clean tar acids. The clean tar acids may be produced with only a slight increase in operating expenses and will bring a price on the market which, under ordinary conditions, will more than offset the added cost .of producing them.

I claim:

l. In the operation of the by-product recovery system of a coal carbonization plant, the process which comprises cooling the hot fresh coal carbonization gases in successive steps, one step being regulated to separate a heavy tar and flushing the cooler with tar or pitch during the separation of heavy tar, While retaining in the gases a substantial quantity of pitch constituents, separating in a subsequent step a tarry oil containing such pitch constituents, distilling the tarry oil to pitch, and blending the pitch with Y the heavy tar.

2. The process of operating the 'ny-product recovery system of a coke oven plant, which comprises cooling the coke oven gases in successive -stages to produce fractional condensates comprising a heavy tar containing only part of the pitch constituents carried by the hot gases and a lighter tar or tarry oil containing additional pitch constituents caried by the hot gases, distilling the tarry oil to pitch, blending the pitch with the heavy tar, and maintaining the mixture of tar and pitch in a heated condition until it is subsequently burned as a fuel.

v 3. The process of operating the by-prcduct recovery system of a coke oven plant, which comprises cooling the coke oven gases in successive stages to produce fractional condensates comprising a heavy tar containing only part of the'pitch constituents carried by the hot gases andy a lighter tar or tarry oil containing additional pitch constituents carried by the hot gases,

distilling the tarry oil\to pitch, blending the pitch with the heavy tar by directing a stream of the heavy tar against a stream of the pitch, collecting the mixture, supplying heat to it to maintain it in a thinly fluid condition until it is drawn off in a thinly fluid condition and utilized as fuel.

4. The method of operating the by-product recovery system of a` coke oven plant, which comprises collecting the gases from the various ovens in a gas-collector main, cooling the gases in the collector main and separating a heavy tar containing only part of the pitch constituents carried by the hot gases, cooling the gases leaving the collector main and separating a tarry oil containing pitch constituents carried by the hot gases therefrom, separately collecting the heavy tar andthe tarryv oil', distilling the tarry oil to pitch and blending the resulting pitch with the heavy tar.

5. The method. of operating the ley-product recovery system 'of a coke oven plant, which comprises collecting the gaaes from a' plurality Aof ovens in a gas-collector main, subjecting the gases therein to regulated cooling and separating a heavy tar containing only part of the pitch constituents carried by the hot gases, withdrawing the heavy tar, cooling the resulting gases to separate a tarry oil therefrom or relatively higher tar acid content than the heavy tar and containing additional pitch constituents carried by the hot gases, separately collecting the tarry oil, distilling the tarry oil to pitch, extracting the distillate With an aqueous alkaline solution to recover tar acids and blending the resulting neutral oil with the pitch and the heavy tar.

6. The method of operating the lay-product recovery system of a 'coke oven plant, which comprises collecting the gases from a plurality of ovens in a gas-collector main, cooling the gases in the main and separating a heavy tar containing only part of the pitch constituents carried by the hot gases, further cooling the resulting gases to separate a tarry oil containing pitch constituents carried by the hot gases therefrom, separately collecting the heavy tar and the tarry oil, d istilling the tarry oil to produce a pitch of high melting point in the neighborhocd of 400 F., intimately mixing and blending the pitch While still hot with tar and utilizing the blended mixture While hot and in a thinly fluid condition as fuel.

7. The method of producing fuel, which comprises collecting in a gas-collector main the gases from a plurality of coke ovens in which coal is being distilled, cooling the gases therein and separating a heavy tar containing only part of the pitch constituents carried by the hot gases, cooling the remlting gases to separate a tarry oil containing pitch constituents carried by the hot gases therefrom, separately collecting the heavy tar and tarry oil, maintaining the tarry oil apart from the heavy tar and distilling oi from the tarry oil volatile oils including the major portion of tar acids to produce pitch, cooling the resulting vapors to produce a clean distillate, extracting said distillate for the removal of tar acids, and blending the resulting neutral oil with the pitch and heavy tar to produce a fuel.

Locale@ t. The method of operating the by-product recovery system of a colte oven plant,l which comprises collecting the gases from a plurality of ovens, in a gas-collector main, subjecting the gasesl toregulated cooling therein, whereby a heavy-tar' containing only part of the pitch constituents carried by the hot gases is' separated from the gases, cooling the resulting gases to separate a tarry oil containing pitch constituents carried by the hot gases therefrom, separately collecting the heavy tar `and the tarry oil, distilling the tarry oil to pitch of a melting vpoint of at least 350 F., and so recovering thedistillate as to obtain a distillate of higher boiling range and a distillate of lower boiling range, extracting the distillate of lower boiling range to obtain tar acids and thus produce a neutral oil, blending the neutral oil with the distillate lof higher boiling range and tar produced directly from the gases to form a creosoting composition,l

and blending the pitch and heavy tar for fuel.

9. The method of producing fuel, which comprises collecting in a gas collector main the gases from a plurality of coke ovens in which coal is being distilled, maintaining a streamof the tar in the bottom of the collector main to ilush the main While cooling the gases to separate heavy tar containing only part of the pitch constituents carried by the hot gases, withdrawing heavyy tar from the main, cooling the resulting gases further to separate a tarry oil containing pitch constituents carried by the hot gases, separately collecting the tarry oil, disitilling it to produce pitch, and blending the pitch with the heavy tar to produce a fuel.

l0. The method of operating the by-product recovery system of a coke oven plantwhich comprises fractionally cooling a portion of the coke oven gases to obtain a heavy tar containing only part of the pitch constituents carried by the hot gases and a tarry oil containing additional pitch constituents carried by the hot gases, distilling the tarry oil to pitch by bringing it into intimate vcontact with other hot coke oven gases, and blending the pitch with the heavy tar.

1l. In the by-product recovery system of a coke oven plant, a collector main, means for withdrawing and separately collecting heavy tar from the collector main, a condensing-system,

. means for withdrawing and separately collecting tarry oil from the condensing system, a still adapted for the distillation of tarry oil and production of pitch, means for conveying tarry oil to the still and withdrawing pitch therefrom,

and apparatus for blending the pitch and the' heavy tar from the collector main.

l2. In combination with the coke oven plant,

' .a collector main connected with a plurality of pipe for conveying terry oil from the condenser t0 the Still, a 'fm1' with heavy tar from the collector main means for conveying heavy tar from the collector main to the mixing device, a vpitch draw-a from the still to the mixing device, a condenser for ecol ing the vapors from the stili and a tar acid extraction teni: for treating the distillate to obtain tar acids therefrom.

13. In combination with a vcolte oven plant, a

collector main connected. with a plurality of `denser to the still. a condenser for cooling the vapors from the still, a tar acid extraction tank for treating the distillate-to obtain tar acids therefrom, means for conveying the distillate to the extraction tank, and `Ameans for conveying the pitch and neutral oil andheavy tar from the still, the extraction tank and the collector main respectively to a mixing tank and means for mixing them therein.

14. In combination with a coke over plant. fractional coolers for obtaining a heavy tar and a tarry oil from coke oven gases from a portion of the coke ovens of the plant, a still, a pipe for conveying the tarry oil from the Larry oil cooler to the still. means for conveying hot coke oven gases from other coke ovens thru the still, means for bringing the tarry oil and gases into intimate contact in the still, .coolers for condensing oils from the gases leaving the still, a mixing tank, a pitch draw-on from the still to the mixing tank and means for conveying the heavy tar to the mixing tank.

15..'I'he method oi producing fuel oil, which comprises distilling l in a plurality of coke ovens, comb the hot coal distillation gases from the ovens and then cooling them as they are combined to separate a'heavy tar, further cooling the resulting combined gases to separate a terry oil, distilling the tarry oil to pitch with a melting point of at least 35il F., and blending thisr pitch while still hot with heavy tar to produce fuel..

16. In the operation of the 'by-product recovery system of a coal carbonization plant, the process which comprises cooling the hot fresh coal carbonization gases in successive steps, one step being regulated to separate a heavy tar and ilushing the cooler withv tar or pitch during the separation of heavy tar, while retaining in the gases a substantial quantity of pitch constituents, separating in a subsequent step a tarry oil containing such pitch constituents, distilling the tan'y oil apart from the heavy tar so as to produce distillate oils from the tarry oil, and blending the pitch constituents with the heavy tar.

S. P. MILLER. 

